Latest Research on The Microbiome and Fertility: Why We Need to Look Beyond Just One Partner

The microbiome is becoming an increasingly interesting area of fertility research, and new research is giving us more insight into just how complex the relationship between our microbes and reproductive health may be.

A recent landmark study published in The Lancet looked at the gut, vaginal and seminal microbiomes of couples undergoing IVF, as well as couples experiencing recurrent pregnancy loss.

And one of the biggest takeaways?

We need to stop looking at fertility through the lens of just one partner, or just one microbiome.

What did the researchers find?

The study identified some interesting associations between microbiome health and reproductive outcomes.

Seminal microbiome

One of the most interesting findings was around the seminal microbiome.

Seminal dysbiosis, an imbalance in the microorganisms present in semen, was associated with a longer time to live birth and a higher risk of pregnancy loss.

In the IVF group, live birth occurred in 57% of couples where seminal dysbiosis was present, compared with 85% where it wasn't.

This is an important finding because it reinforces why male fertility shouldn't be overlooked when couples are experiencing fertility difficulties or poor IVF outcomes.

Sperm health is about much more than sperm count and motility. We're increasingly understanding that the environment in which sperm develop may matter too.

The gut microbiome

The researchers also found that increasing levels of gut dysbiosis in women who were doing IVF or struggling with recurrent pregnancy loss were associated with a longer time to live birth and lower pregnancy establishment.

The gut microbiome has a role far beyond digestion. It interacts with the immune system, metabolism and inflammation, and may also influence how the body processes and recycles hormones.

This doesn't mean that an “unhealthy gut” causes infertility, but it does give us another reason to consider gut health as part of the bigger picture when supporting fertility.

What about the vaginal microbiome?

Interestingly, vaginal dysbiosis alone wasn't consistently associated with reproductive outcomes in this study.

This is particularly important because there has been a lot of attention around the vaginal microbiome and fertility in recent years.

It highlights just how complex this area is.

We can't simply say that a particular microbiome profile equals a particular fertility outcome. The gut, vaginal and seminal microbiomes are interconnected, and their relationship with fertility is likely to be influenced by many other factors too.

What does this mean if you're trying to conceive?

This research doesn't mean that everyone trying to conceive always needs vaginal, gut and seminal microbiome testing or treatment.

In fact, I think it's really important that we don't take one interesting study and turn it into another fertility “must-do”. A personalised approach should always be taken.

This study demonstrates associations, not proof of causation.

In other words, we can't conclude from these findings that dysbiosis directly causes infertility, miscarriage or poor IVF outcomes.

But it does give us another reason to think more broadly when someone is experiencing:

🤍 Unexplained infertility

🤍 Recurrent pregnancy loss

🤍 Repeated implantation failure

🤍 Poor IVF outcomes

🤍 Abnormal sperm parameters

Depending on your individual history, this might mean considering the gut and reproductive microbiomes alongside other areas such as:

• Nutrition and nutrient status

• Hormonal health

• Inflammation

• Metabolic health

• Sperm health

• Lifestyle

• Medical and reproductive history

  
  

Fertility is a two-person journey

One of the things I find particularly interesting about this research is that it reinforces something we already know: fertility involves both partners.

It can be very easy for investigations to become focused primarily on the woman, particularly when it comes to IVF or recurrent pregnancy loss.

But sperm contributes half of the embryo's genetic material, and we're learning more about the role that male reproductive health, including the seminal environment, may play in reproductive outcomes.

Looking at both partners can therefore be an important part of a more comprehensive approach.

So, should we always test the gut, vaginal and seminal microbiomes?

Not necessarily.

Microbiome testing is an area of growing research, but we're still learning about what constitutes a “healthy” microbiome, how much it varies between individuals and, importantly, which interventions actually improve fertility outcomes.

For many couples trying to conceive, particularly if they have experienced failed rounds of IVF or recurrent pregnancy loss, testing may be worth considering. For others, focusing on the foundations, a nutrient-dense diet, adequate fibre, good-quality protein, healthy fats, sleep, movement and overall metabolic health, may be a more appropriate place to start.

As with so much in fertility, context matters.

There isn't one test, supplement or dietary change that is going to be right for everyone.

The bigger picture

The microbiome is an exciting area of fertility research, but we're still at the beginning of understanding exactly how these microorganisms interact with reproductive health.

What this study does give us is another reason to take a whole-person, whole-couple approach to fertility.

Rather than looking at one symptom, one partner or one microbiome in isolation, we can start to consider how different aspects of health may interact, and where personalised support could be helpful.

Research continues to move this area forward, and I'll certainly be keeping a close eye on what comes next.

If you're experiencing unexplained infertility, recurrent pregnancy loss, repeated implantation failure or poor IVF outcomes and wondering whether the microbiome could be relevant to you, this is something you can discuss with us directly via a complimentary call.

Reference

Behrendt-Møller I, Krog M, Myers P et al. Gut, vaginal, and seminal microbiomes in couples with infertility or recurrent pregnancy loss: a two-cohort prospective study of reproductive outcomes

The Lancet Obstetrics, Gynaecology, & Women’s Health, 2026